Responses to affective pictures depicting humans: late positive potential reveals a sex-related effect in processing that is not present in subjective ratings.

We examined sex-related effects in the amplitudes of the late positive potential (LPP), an event-related potential elicited by the presentation of emotional stimuli. Sixteen females and 18 males viewed emotional pictures to perform a visual detection task. In female participants, viewing unpleasant pictures elicited larger LPP (550-900 ms) when the pictures contained humans (human pictures) than when they did not contain humans (non-human pictures). For male participants, the results were reversed, with smaller LPP for unpleasant human pictures. Subjective ratings of valence in both female and male participants showed that unpleasant human pictures were evaluated less negatively than unpleasant non-human pictures. The results indicate that greater LPP amplitude for human than for non-human pictures occurred in females irrespective of subjective evaluations. This suggests that relatively robust processes in females cause sex-related effects in sensitivity to human pictures.